1. Field of the Invention
The present invention relates to a control device.
2. Description of the Related Art
In scanning exposure apparatuses or gantry-type machine tools, the positions of a plurality of moving members or the positions of a plurality of control axes with high accuracy are to be synchronously controlled. Therefore, conventionally, master-slave synchronization control has been performed. In the master-slave synchronization control, one of a plurality of moving members serves as a master, the other moving members serve as slaves, and the slaves follow the displacement of the master when a disturbance occurs in the master. In this way, the accuracy of synchronization is improved. The disturbance that occurs in the slaves is reduced by the control of the slaves.
In addition, bilateral synchronization control has been proposed to further improve the accuracy of synchronization between a wafer stage and a reticle stage (Japanese Patent Application Laid-Open No. 08-241126). In the bilateral synchronization control, the master and the slave are operated such that they both simultaneously compensate the synchronization error, without discriminating one from another, when disturbances occur in either one of control targets. In addition, Japanese Patent Application No. 2006-310849 discusses master-slave synchronization control to which iterative learning control is applied.
It is considered that the synchronization performance of the bilateral synchronization control (or similarly multi-lateral synchronization control for two or more control axes) may be better than that of the master-slave synchronization control. However, a control system of the former has a complicated structure, and it is difficult to derive or adjust the control system. As a result, it is difficult to improve the accuracy of synchronization.